E. El-magd et M. Brodmann, Influence of precipitates on ductile fracture of aluminium alloy AA7075 athigh strain rates, MAT SCI E A, 307(1-2), 2001, pp. 143-150
Under dynamic loading, the stabilising effect of the material's increased s
train rate sensitivity leads to an increase in ductility. At the starting p
oint of necking, the local strain rate increases resulting in a correspondi
ng increase of local flow stress within the neck zone. Therefore, other reg
ions of the specimen undergo additional plastic deformation and the necking
process is shifted to high strain values. On the other. hand, an increased
strain rate reduces the local fracture strain, leading to an increased dyn
amic notch sensitivity. Notches are often the starting point for ductile fr
acture caused by impact. This kind of failure occurs due to nucleation, gro
wth and coalescence of voids around inhomogeneities, such as inclusions and
precipitations. Therefore, dynamic and quasi-static tension tests were car
ried out on smooth and notched specimens of age-hardenable aluminium alloy
AA7075. Using different heat treatment conditions, the influence of size, v
olume fraction and distribution of particles on the fracture strain were in
vestigated. Tests with various notch geometries allow the influence of the
degree of multiaxiality to be analyzed. By combining experiment and numeric
al simulation, the location of void initiation has been estimated and the i
nfluence of strain rate on the local fracture strain has been determined. (
C) 2001 Elsevier Science B.V. All rights reserved.